Semiconductor device

Abstract

A semiconductor device includes a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type on the first semiconductor region, a third semiconductor region of the first conductivity type on the second semiconductor region, a control electrode disposed within and insulated from the first, second, and third semiconductor regions, a first electrode electrically connected with the second and third semiconductor regions, a second electrode, and a fourth semiconductor region of the second conductivity type between the second electrode and the first semiconductor region. The fourth semiconductor region includes a first portion having a first dopant concentration and a second portion having a second dopant concentration higher than the first dopant concentration, and a contact area of the first portion with the second electrode is larger than a contact area of the second area with the second electrode.

What is claimed is: 
     
       1. A semiconductor device comprising:
 a first semiconductor region of a first conductivity type; 
 a second semiconductor region of a second conductivity type on the first semiconductor region; 
 a third semiconductor region of the first conductivity type on the second semiconductor region; 
 a control electrode disposed within the first and second semiconductor regions; 
 an insulating film between the control electrode and the first and second semiconductor regions; 
 a first electrode electrically connected with the second semiconductor region and the third semiconductor region; 
 a second electrode; and 
 a fourth semiconductor region of the second conductivity type between the second electrode and the first semiconductor region and electrically connected with the second electrode, the fourth semiconductor region including a first portion having a first dopant concentration and a second portion having a second dopant concentration higher than the first dopant concentration, wherein an area of contact of the first portion with the second electrode is larger than an area of contact of the second area with the second electrode. 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein when an electric current smaller than a saturation current flows between the first electrode and the second electrode, carriers are injected into the first semiconductor region mostly from the first portion, and
 when the saturation current flows between the first electrode and the second electrode, the carriers are injected into the first semiconductor region from the first portion and the second portion. 
 
     
     
       3. The semiconductor device according to  claim 2 , wherein a relationship S2/(S1+S2)≦Irc/Isc is satisfied, where S1 represents the first contact area, S2 represents the second contact area, Irc represents a rated current of the semiconductor device, and Isc represents a saturation current of the semiconductor device. 
     
     
       4. The semiconductor device according to  claim 3 , wherein S2/(S1+S2) is equal to or smaller than ⅕. 
     
     
       5. The semiconductor device according to  claim 4 , wherein
 the first dopant concentration is equal to or higher than 1×10 16  cm −3  and equal to or lower than 1×10 18  cm −3 , and 
 the second dopant concentration is equal to or higher than 1×10 18  cm −3  and equal to or lower than 1×10 20  cm −3 . 
 
     
     
       6. The semiconductor device according to  claim 5 , wherein
 the first portion has a longer length in a first direction along a contact surface with the second electrode than the second portion. 
 
     
     
       7. The semiconductor device according to  claim 6 , wherein
 W2/(W1+W2) is equal to or smaller than ⅕, where W1 represents the length of the first portion and W2 represents the length of the second portion. 
 
     
     
       8. The semiconductor device according to  claim 7 , wherein the length of the second portion is equal to or larger than 0.1 micrometers and equal to or smaller than 10 micrometers. 
     
     
       9. The semiconductor device according to  claim 1 , further comprising:
 a fifth semiconductor region of the first conductivity type between the first semiconductor region and the fourth semiconductor region, the fifth semiconductor region having a higher dopant concentration than the first semiconductor region. 
 
     
     
       10. The semiconductor device according to  claim 1 , wherein the control electrode extends between a lower portion of the first semiconductor region and an upper portion of the third semiconductor region and is insulated from the first, second, and third semiconductor region by an insulating layer. 
     
     
       11. A semiconductor device comprising:
 a first semiconductor region of a first conductivity type; 
 a second semiconductor region of a second conductivity type on the first semiconductor region; 
 a third semiconductor region of the first conductivity type on the second semiconductor region; 
 a control electrode disposed within the first and second semiconductor regions; 
 an insulating film between the control electrode and the first and second semiconductor regions; 
 a first electrode electrically connected with the second semiconductor region and the third semiconductor region; 
 a second electrode; and 
 a fourth semiconductor region of the second conductivity type between the second electrode and the first semiconductor region and electrically connected with the second electrode, the fourth semiconductor region including first and second portions arranged along a first direction, the first portion having a first dopant concentration and the second portion having a second dopant concentration higher than the first dopant concentration and a shorter length in the first direction than the first portion. 
 
     
     
       12. The semiconductor device according to  claim 11 , wherein
 the first dopant concentration is equal to or higher than 1×10 16  cm −3  and equal to or lower than 1×10 18  cm −3 , and 
 the second dopant concentration is equal to or higher than 1×10 18  cm −3  and equal to or lower than 1×10 20  cm −3 . 
 
     
     
       13. The semiconductor device according to  claim 12 , wherein
 W2/(W1+W2) is equal to or smaller than ⅕, where W1 represents the length of the first portion and W2 represents the length of the second portion. 
 
     
     
       14. The semiconductor device according to  claim 11 , further comprising:
 a fifth semiconductor region of the first conductivity type between the first semiconductor region and the fourth semiconductor region, the fifth semiconductor region having a higher dopant concentration than the first semiconductor region. 
 
     
     
       15. A semiconductor device comprising:
 a first semiconductor region of a first conductivity type; 
 a second semiconductor region of a second conductivity type on the first semiconductor region; 
 a third semiconductor region of the first conductivity type on the second semiconductor region; 
 a control electrode disposed within the first and second semiconductor regions; 
 an insulating film between the control electrode and the first and second semiconductor regions; 
 a first electrode electrically connected with the second semiconductor region and the third semiconductor region; 
 a second electrode; and 
 a fourth semiconductor region of the second conductivity type between the second electrode and the first semiconductor region and electrically connected with the second electrode, the fourth semiconductor region including a first portion having a first dopant concentration and a second portion having a second dopant concentration higher than the first dopant concentration, wherein an area of contact of the first portion with the second electrode is larger than an area of contact of the second area with the second electrode, and a height of the first portion in a direction that extends from the second electrode to the first electrode is smaller than a height of the second portion in the same direction. 
 
     
     
       16. The semiconductor device according to  claim 15 , wherein
 the first dopant concentration is equal to or higher than 1×10 16  cm −3  and equal to or lower than 1×10 18  cm −3 , and 
 the second dopant concentration is equal to or higher than 1×10 18  cm −3  and equal to or lower than 1×10 20  cm −3 . 
 
     
     
       17. The semiconductor device according to  claim 16 , wherein
 W2/(W1+W2) is equal to or smaller than ⅕, where W1 represents a length of the first portion in a direction along a contact surface with the second electrode and W2 represents a length of the second portion in a direction along a contact surface with the second electrode. 
 
     
     
       18. The semiconductor device according to  claim 15 , further comprising:
 a fifth semiconductor region of the first conductivity type between the first semiconductor region and the fourth semiconductor region, and the fifth semiconductor region having a higher dopant concentration than the first semiconductor region. 
 
     
     
       19. The semiconductor device according to  claim 18 , wherein the first portion is in contact with the fifth semiconductor region and the second portion is not in contact with the fifth semiconductor region. 
     
     
       20. The semiconductor device according to  claim 15 , wherein the first portion is in contact with the first semiconductor region and the second portion is not in contact with the first semiconductor region.